Purpose: Evidence is scarce regarding the associations of romantic orientation with mental health and personality. The aims of the present study, therefore, were to examine psychological distress among homoromantic, biromantic, and heteroromantic adults and to investigate how personality dimensions influence their distress. Methods: A cross-sectional survey study was conducted between August 2018 and January 2021. Psychological distress, personality, and romantic orientation were assessed with the 6-item Kessler Psychological Distress Scale (K6), the Ten-Item Personality Inventory (TIPI), and a question about romantic orientation, respectively, in a web-based survey distributed to 11,922 participants. Saliva samples were collected for DNA extraction. After excluding those who did not cluster with Japanese ancestry and those whose genotypic sex did not match their reported sex, 11,662 individuals were included in further analyses. Results: The prevalence of being homoromantic or biromantic was 1.0% and 2.0% for females and 1.5% and 1.2% for males, respectively. Homoromantic males, but not females, had significantly higher K6 scores than their heteroromantic counterparts. Both male and female biromantic participants had significantly higher K6 scores than their heteroromantic counterparts. Furthermore, a significant association was found between romantic orientation and TIPI scores. Accounting for personality profiles did not alter the observed association between romantic orientation and psychological distress. Conclusion: Biromantic adults and homoromantic male adults of genetically confirmed Japanese ancestry living in Japan experienced higher psychological distress than heteroromantic individuals. The mental health disparities of the romantic minority individuals were irrespective of their personality profiles, suggesting the involvement of other factors such as minority stress in Japan.
Keywords: LGB persons; personality; romantic orientation; sexual and gender minority; sexual orientation.